On-board load weighting systems for vehicles such as logging trucks are well-known to the prior art. An example of such a system is that disclosed and claimed in U.S. Pat. No. 3,661,220, May 9, 1972, Harris, and assigned to the assignee of the present invention. A plurality of load cell bodies, each consisting of a machined rectangular steel block, are supported between load-carrying members and tractor and trailer frames of the logging truck. In each load cell body there is formed first and second end slots which serve to direct the load, applied by the load-carrying member to a top surface of the load cell body, to a central portion of the load cell body and also, in conjunction with means supporting the load cell body above the tractor or trailer frame, to define first and second beams which are accordingly deflected in response to the load. The amount of stress in the first and second beams is measured by strain gages located along a longitudinal surface of the load cell body which, when connected in an appropriate circuit, provide an output signal proportional to the amount of applied load.
Systems of the type described in the aforementioned Harris patent have met with considerable commercial success in the logging truck industry, inasmuch as such systems provide highly accurate and repeatable measurements of logging loads under adverse terrain and environmental conditions. However, such systems have been subject to a number of malfunctions in actual operation resulting from cracks appearing in, and other structural failures of, the load cell body. Because logging trucks in operation encounter severe off-road terrain conditions, it was first thought that these structural failures were due to inadequate strength in the load cell body. Although the number and frequency of occurrence of load cell structural failures was reduced by redesign and strengthening of the load cell body, such structural failures continued to occur in sufficient numbers to present a serious problem inasmuch as any such structural failure requires replacement of the load cell body which is a costly part of the on-board load weighing system.
It is therefore an object of this invention to provide an improved on-board load weighing system.
It is a further object of this invention to provide such an improved on-board load weighing system in which the number and frequency of occurrence of structural failures of the load cells therein is significantly reduced from that encountered with the systems of the prior art.
It is yet a further object of this invention to provide an improved load cell for use in on-board load weighting systems which has a decreased susceptibility of structural failure in normal operation, as compared with the load cells of the prior art.
It is another object of this invention to provide a means for reducing the number and frequency of occurrence of structural failures of load cells utilized in existing and new on-board load weighing systems.